JP7803097B2 - Soft magnetic alloy ribbon, manufacturing method thereof, magnetic core, and component - Google Patents

Description

This disclosure relates to soft magnetic alloys, soft magnetic alloy ribbons and their manufacturing methods, magnetic cores, and components.

Soft magnetic alloys with a nanocrystalline structure offer excellent magnetic properties and are used in transformers, electronic components, motors, and other devices. These transformers, electronic components, and motors are required to be smaller and more efficient. Therefore, the soft magnetic alloys used in these components (transformers, electronic components, motors, etc.) are required to have even better properties. The required properties of such soft magnetic alloys include high saturation magnetic flux density and low iron loss. Many of these components are being miniaturized by increasing their operating frequencies in response to the trend toward higher frequencies in semiconductors and other devices. Fe-based amorphous alloys and Fe-based nanocrystalline alloys, which have low iron loss, are attracting attention. Furthermore, for commercial adoption, soft magnetic alloys with excellent cost, productivity, and heat treatability are required.

Patent Document 1 describes a method for producing a soft magnetic material that achieves both high saturation magnetization and low coercive force, by heating an alloy having an amorphous phase and a composition of the composition formula Fe _{100-ab-c Ba} Cu _{b M'c} , where M' is at least one element selected from Nb, Mo, Ta, W, Ni, and Co, satisfying 10≦a≦16, 0<b≦2, and 0≦c≦8, at a heating rate of 10°C/sec or more, and holding the alloy at a temperature equal to or higher than the crystallization start temperature and lower than the temperature at which an Fe—B compound is generated, for 0 to 80 seconds.

In Patent Document 2, the composition formula ((Fe _(1-(α+β)) X1 _α X2 _β ) _{(1-(a+b+c+d+e))} B _a Si _b C _c Cu _d M _{The publication} discloses a soft magnetic alloy consisting of X1, Co, Ni, and Ni; X2, Al, Mn, Ag, Zn, Sn, As, Sb, Bi, N, O, and rare earth elements; M, Hf, Zr, Ta, Ti, Mo, W, and V; and 0.140<a≦0.240, 0≦b≦0.030, 0<c<0.080, 0<d≦0.020, 0≦e≦0.030, α≧0, β≧0, and 0≦α+β≦0.50. The publication also discloses that this soft magnetic alloy simultaneously possesses high saturation magnetic flux density, low coercive force, and high magnetic permeability μ'.

Patent Document 3 discloses a soft magnetic alloy represented by Fe _100-x-y-z A _x M _y X _z , where A is at least one element selected from Cu and Au, M is at least one element selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, and X is at least one element selected from B and Si, and the atomic percentages are 0<x≦5, 0.4≦y<2.5, and 10≦z≦20, and the soft magnetic alloy has a saturation magnetic flux density of 1.7 T or more and a coercive force of 15 A/m or less.

International Publication No. 2018/025931 JP 2019-94532 A WO 2008/133301

Patent Document 1 discloses a method for producing a soft magnetic material with high saturation magnetization. However, the soft magnetic material described in Patent Document 1 does not contain Si. Therefore, with the soft magnetic material described in Patent Document 1, a _SiO2 film that contributes to corrosion resistance is not formed on the material surface, making it difficult to prevent rust and the like.

The soft magnetic alloy described in Patent Document 2 does not have a very high saturation magnetic flux density (Bs). Generally, the saturation magnetic flux density increases as the Fe content increases, but in Example 6, where the Fe content is 84.0 at%, the saturation magnetic flux density (Bs) is 1.76 T. Furthermore, since Example 6 does not contain Si, the above-mentioned issues arise. Furthermore, the soft magnetic alloy described in Patent Document 2 is thought to have insufficient heat treatability due to its relatively high B content.

The soft magnetic alloy described in Patent Document 3 is expensive because it contains a large amount of expensive M elements (such as Nb). Furthermore, it is anisotropic in the casting direction, and the ratio of the magnetic flux density when a magnetic field of 80 A/m is applied in the casting direction to the magnetic flux density when a magnetic field of 80 A/m is applied in a direction perpendicular to the casting direction is large, making it unsuitable for applications requiring isotropy.

The present disclosure preferably provides a soft magnetic alloy having a high saturation magnetic flux density and low core loss, a soft magnetic alloy ribbon made of the soft magnetic alloy and a method for manufacturing the same, and a magnetic core and component using the soft magnetic alloy ribbon.

Specific means for solving the above problems include the following aspects.
<1> _{A soft magnetic alloy} represented by the composition formula (Fe1 _{-xAx ) aSibBcCudMe} , where A is at least one of Ni and Co, and M is at least one selected from the group consisting of Nb, Mo, V, Zr, Hf, and W, and where the atomic percentages are 82.4≦a≦86, 0.2≦b≦2.4, 12.5≦c≦15.0, 0.05≦d≦0.8, 0.4≦e≦1.0, and 0≦x≦0.1,
The soft magnetic alloy has a structure in which crystal grains of 60 nm or less exist in an amorphous phase.
<2> The soft magnetic alloy according to <1>, wherein the saturation magnetic flux density is 1.74 T or more.
<3> In <1> or <2>, the soft magnetic alloy has a density of 7.45 g/cm ³ or more.
<4> _A soft magnetic alloy ribbon having an alloy composition represented by _a composition formula ( _{Fe1 -xAx ) aSibBcCudMe} , _wherein A is at least one of Ni and Co, and M is at least one selected from the group consisting of Nb, Mo, V, Zr, Hf, and W, and the atomic percentages of the soft magnetic alloy ribbon are 82.4≦a≦86, 0.2≦b≦2.4, 12.5≦c≦15.0, 0.05≦d≦0.8, 0.4≦e≦1.0, and 0≦x≦0.1,
The soft magnetic alloy ribbon has a structure in which crystal grains having a grain size of 60 nm or less exist in an amorphous phase, and has a saturation magnetic flux density of 1.74 T or more and an iron loss at 1 kHz and 1 T of 25 W/kg or less.
<5> The soft magnetic alloy ribbon according to <4>, wherein the density is 7.45 g/cm ³ or more.
<6> The soft magnetic alloy ribbon according to <4> or <5>, wherein the space factor is 86% or more.
<7> The soft magnetic alloy ribbon according to any one of <4> to <6>, having a thickness of 25 μm or more.
<8> The soft magnetic alloy ribbon according to any one of <4> to <7>, wherein a ratio (L/W) of a magnetic flux density L when a magnetic field of 80 A/m is applied in a casting direction of the soft magnetic alloy ribbon to a magnetic flux density W when a magnetic field of 80 A/m is applied in a direction perpendicular to the casting direction of the soft magnetic alloy ribbon is 0.7 to 1.3.
<9> The soft magnetic alloy ribbon according to any one of <4> to <8>, wherein the soft magnetic alloy ribbon has a saturation magnetostriction of 20 ppm or less.
<10> A manufacturing method for obtaining a soft magnetic alloy ribbon according to any one of <4> to <9>,
A method for producing a soft magnetic alloy ribbon having a structure in which crystal grains having a grain size of 60 nm or less exist in an amorphous phase by heat-treating an alloy ribbon,
In the heat treatment, a temperature T1 is set to be 10 to 140°C lower than the bccFe crystallization start temperature, and a temperature T2 is set to be 30 to 120°C lower than the FeB compound precipitation start temperature.
Heat from room temperature to temperature T1 at a temperature increase rate of 50°C/sec or more,
Heating from temperature T1 to temperature T2 at a temperature rise rate that is slower than the temperature rise rate up to temperature T1 and is 400° C./sec or less,
Cooling after reaching temperature T2, or
After reaching temperature T2, the soft magnetic alloy ribbon is held at a temperature between temperature T2-50°C and temperature T2 for 0.5 to 60 seconds, and then cooled.
<11> The method for producing a soft magnetic alloy ribbon according to <10>, wherein the alloy ribbon before the heat treatment is obtained by ejecting a molten alloy onto a rotating chill roll and rapidly solidifying it on the chill roll, and an outer periphery of the chill roll is made of a Cu alloy having a thermal conductivity of 120 W/(m K) or more.
<12> The method for producing a soft magnetic alloy ribbon according to <10> or <11>, wherein M2/M1 is 1.005 or more, where M1 is a density of the alloy ribbon before the heat treatment and M2 is a density of the alloy ribbon after the heat treatment.
<13> A magnetic core formed using the soft magnetic alloy ribbon according to any one of <4> to <9>.
<14> A component comprising the magnetic core according to <13> and a winding.

According to one aspect of the present disclosure, it is possible to obtain a soft magnetic alloy and a soft magnetic alloy ribbon having a high saturation magnetic flux density and low core loss. Furthermore, according to one aspect of the present disclosure, it is possible to obtain a soft magnetic alloy ribbon having isotropy. Furthermore, according to a magnetic core and a component using the soft magnetic alloy ribbon of one aspect of the present disclosure, it is possible to obtain a magnetic core and a component having a high saturation magnetic flux density and low core loss characteristics.

1A and 1B are diagrams showing an example of a heat treatment pattern according to an embodiment of the present disclosure and a reference example of a heat treatment pattern. FIG. 10 is a correlation diagram of the holding temperature, B ₈₀₀₀ , and iron loss of samples heat-treated according to the heat treatment pattern of the reference example. FIG. 10 is a correlation diagram of the holding temperature, B ₈₀₀₀ , and iron loss of a sample heat-treated according to a heat treatment pattern of an embodiment of the present disclosure. 1 is a transmission electron microscope image of a soft magnetic alloy ribbon No. 2 according to an embodiment of the present disclosure.

Embodiments of the present disclosure are described in detail below. The present disclosure is not limited to the following embodiments and can be implemented with appropriate modifications within the scope of the purpose of the present disclosure.

In the present disclosure, a numerical range indicated using "to" indicates a range that includes the numerical values before and after "to" as the lower and upper limits, respectively. In the numerical ranges described in stages in the present disclosure, the upper or lower limit described in a certain numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in the numerical ranges described in the present disclosure, the upper or lower limit described in a certain numerical range may be replaced with a value shown in the examples.
In the present disclosure, a combination of two or more preferred aspects is a more preferred aspect.

The soft magnetic alloy of the present disclosure is represented by a composition formula ( _{Fe1 -xAx ) aSibBcCudMe} , _where A is at least one of Ni and Co, _and M is one or more selected from the group consisting of Nb, Mo, V, Zr, Hf, and W _, and the atomic percentages are 82.4≦a≦86, 0.2≦b≦2.4, 12.5≦c≦15.0, 0.05≦d≦0.8, 0.4≦e≦1.0, and 0≦x≦0.1,
The soft magnetic alloy has a structure in which crystal grains with a grain size of 60 nm or less exist in an amorphous phase.

First, the composition of the present disclosure will be described in detail below.
The content of Fe (iron) is preferably 82.4% or more and 86% or less in atomic percent.
By setting the Fe content to 82.4% or more, it is possible to achieve a saturation magnetic flux density of 1.74 T or more. The Fe content is preferably 83% or more, more preferably 83.5% or more, and even more preferably 84% or more.
Furthermore, if the Fe content exceeds 86%, it becomes difficult to form an amorphous structure, so the Fe content is set to 86% or less, preferably 85.5% or less.

In the composition of the present disclosure, a portion of the Fe may be substituted with at least one element selected from Ni and Co. In this case, the composition can be expressed as (Fe _1-x A _x ), where A is at least one element selected from Ni and Co, and x is 0.1 or less. Note that x may be 0. When a portion of the Fe is substituted with at least one element selected from Ni and Co, the above-described range of Fe can be interpreted as the range of (Fe _1-x A _x ). In other words, (Fe _1-x A _x ) is 82.4% or more and 86% or less in atomic percent. Preferably, it is 83% or more, more preferably 83.5% or more, and even more preferably 84% or more. Also, it is preferably 85.5% or less.

The content of Si (silicon) is 0.2% or more and 2.4% or less in atomic percent.
By including Si, an _SiO2 oxide film several tens of nanometers thick can be formed on the alloy surface, thereby improving the corrosion resistance of the soft magnetic alloy. To achieve this effect of improving corrosion resistance, the Si content is set to 0.2% or more, preferably 1.0% or more.
If the Si content exceeds 2.4%, it becomes difficult to obtain a saturation magnetic flux density of 1.74 T or more, and it also becomes difficult to increase the thickness of the soft magnetic alloy ribbon. Therefore, the Si content is set to 2.4% or less, preferably 2.0% or less, and more preferably 1.9% or less.

The content of B (boron) is 12.5% or more and 15.0% or less in atomic percent.
If the B content is less than 12.5%, it becomes difficult to form an amorphous phase, so the B content is set to 12.5% or more, preferably 13.0% or more, and more preferably 13.5% or more.
If the B content exceeds 15.0%, the difference between the bccFe (αFe) crystallization onset temperature and the FeB compound precipitation onset temperature becomes small, narrowing the optimum heat treatment temperature range. This makes it difficult to obtain a uniform, fine nanocrystalline structure and to achieve an iron loss of 25 W/kg or less at 1 T and 1 kHz. For this reason, the B content is set to 15.0% or less. It is preferably 14.5% or less, more preferably 14.4% or less, and even more preferably 14.0% or less.

The content of Cu (copper) is 0.05% or more and 0.8% or less in atomic percent.
If the Cu content is less than 0.05%, it becomes difficult to obtain a uniform and fine nanocrystalline structure, and it becomes difficult to keep the iron loss at 1 T, 1 kHz to 25 W/kg or less. Therefore, the Cu content is set to 0.05% or more, preferably 0.2% or more, more preferably 0.4% or more, and even more preferably 0.5% or more.
If the Cu content exceeds 0.8%, the soft magnetic alloy ribbon becomes easily embrittled, making it difficult to increase the thickness of the soft magnetic alloy ribbon. Therefore, the Cu content is set to 0.8% or less, and preferably 0.7% or less.

The element M is at least one element selected from the group consisting of Nb, Mo, V, Zr, Hf and W, and is present in an amount of 0.4% to 1.0% in atomic percent.
The M element can shift the temperature at which the precipitation of FeB compounds, which significantly deteriorates magnetism, begins to increase. This widens the difference between the bccFe (αFe) crystallization start temperature and the FeB compound precipitation start temperature, which has the effect of widening the range of optimal heat treatment temperatures and easing the heat treatment conditions. Therefore, the M content is set to 0.4% or more. Preferably, it is 0.42% or more, and more preferably, it is 0.43% or more.
The M element is expensive and therefore increases the price. For this reason, a lower content is preferable. Therefore, the content of the M element is set to 1.0% or less. Preferably, it is 0.9% or less, more preferably 0.8% or less, even more preferably 0.7% or less, and even more preferably 0.6% or less.

The soft magnetic alloy of the present disclosure may contain C (carbon). The C content is preferably 1% by mass or less.

Furthermore, the soft magnetic alloy of the present disclosure may contain impurities other than the above-mentioned C in addition to the elements represented by the composition formula (Fe _1-x A _x ) _a Si _b B _c Cu _{d Me} .
Examples of impurities include S (sulfur), O (oxygen), N (nitrogen), Cr, Mn, P, Ti, and Al. For example, the S content is preferably 200 mass ppm or less, the O content is preferably 5000 mass ppm or less, and the N content is preferably 1000 mass ppm or less. The total content of these impurities is preferably 0.5 mass% or less. Furthermore, as long as it is within the above range, elements corresponding to the impurities may be added.

The soft magnetic alloy of the present disclosure has a structure in which crystal grains of 60 nm or less exist in an amorphous phase. This structure in which crystal grains of 60 nm or less exist in an amorphous phase is also called a nanocrystalline structure. Crystals of 60 nm or less in size are also called nanocrystals.
The soft magnetic alloy of the present disclosure is characterized in that it has a nanocrystalline structure.
Furthermore, the soft magnetic alloy of the present disclosure preferably has a nanocrystalline volume fraction of 50% or more. This volume fraction can be roughly calculated by observing the nanocrystalline and amorphous phases, for example, by observing the cross section of the alloy using a transmission electron microscope (TEM). In other words, it is possible to determine whether the nanocrystalline volume fraction is 50% or more from the above observation image.

Furthermore, when observing the cross section of the alloy, it is preferable that, in a specific field of view, the area ratio of crystal grains with a grain size of 60 nm or less is 50% or more (a value where the specific field of view area is 100%). The soft magnetic alloy of the present disclosure comprises crystal grains with a grain size of 60 nm or less and an amorphous phase, and it is preferable that the area ratio of crystal grains with a grain size of 60 nm or less is 50% or more. By observing the cross section of the alloy using, for example, a transmission electron microscope (TEM), it is possible to observe the crystal grains with a grain size of 60 nm or less and the amorphous phase and determine the area ratio.

The soft magnetic alloy of the present disclosure preferably has a saturation magnetic flux density of 1.74 T or more, more preferably 1.75 T or more, and even more preferably 1.77 T or more.
The soft magnetic alloy of the present disclosure preferably has a density of 7.45 g/cm ³ or more. A density of 7.45 g/cm ³ or more increases the volume fraction of nanocrystals, and increases the saturation magnetic flux density.

The soft magnetic alloy of the present disclosure preferably has an iron loss of 25 W/kg or less at 1 kHz and 1 T. Furthermore, this iron loss is preferably 18 W/kg or less. Furthermore, this iron loss is preferably 15 W/kg or less.
Furthermore, the soft magnetic alloy of the present disclosure preferably has a saturation magnetostriction of 20 ppm or less, which makes it easier to obtain isotropy.
According to the soft magnetic alloy of the present disclosure, it is possible to obtain a soft magnetic alloy having a high saturation magnetic flux density and low core loss.

The soft magnetic alloy disclosed herein can be in the form of an alloy ribbon, a pulverized powder obtained by pulverizing the alloy ribbon, or a powder produced using an atomization method, as described below.

The soft magnetic alloy ribbon of the present disclosure can be obtained by ejecting a molten alloy having the above-described soft magnetic alloy composition onto a rotating chill roll, rapidly solidifying the molten alloy on the chill roll to obtain an alloy ribbon, and then heat treating the alloy ribbon.
The molten alloy can be obtained, for example, by blending the element sources (pure iron, ferroboron, ferrosilicon, etc.) that will form the desired alloy composition and heating them to above their melting points in an induction heating furnace or the like.

The molten alloy is ejected from a slit-shaped nozzle of a predetermined shape onto a rotating chill roll, where it is rapidly cooled and solidified to obtain a thin alloy ribbon. The chill roll can have an outer diameter of 350-1000 mm, a width of 100-400 mm, and a peripheral speed of 20-35 m/s. It is preferable that the chill roll be equipped with an internal cooling mechanism (such as water cooling) to suppress temperature rise around the periphery.

It is also preferable that the outer periphery of the chill roll be made of a Cu alloy with a thermal conductivity of 120 W/(m·K) or higher. By making the thermal conductivity of the outer periphery 120 W/(m·K) or higher, the cooling rate when the molten alloy is cast into an alloy ribbon can be increased. This suppresses embrittlement of the alloy ribbon and enables the alloy ribbon to be thickened. It also suppresses surface crystallization during casting, suppresses coarsening of crystal grains during heat treatment of the alloy ribbon, and reduces iron loss. Note that thickening refers to, for example, a thickness of 15 μm or more, preferably a thickness of 20 μm or more.

The thermal conductivity of the outer periphery of the cooling roll is preferably 150 W/(m·K) or more, and more preferably 180 W/(m·K) or more. In particular, when the thickness of the soft magnetic alloy ribbon is 30 μm or more, it is preferable that the thermal conductivity of the outer periphery be 150 W/(m·K) or more.

The outer periphery of the chill roll is the part that comes into contact with the molten alloy, and its thickness should be approximately 5 to 15 mm. The inside of the outer periphery of the chill roll should be made of a structural material that maintains the roll structure.

The molten alloy is rapidly solidified on a cooling roll to produce an alloy ribbon, which is then heat-treated to obtain a soft magnetic alloy ribbon with a nanocrystalline structure. During this heat treatment, it is preferable to heat the alloy ribbon to a temperature equal to or higher than the bccFe (αFe) crystallization onset temperature, while adjusting the temperature so that the alloy ribbon does not reach the FeB compound precipitation onset temperature.

Conventional heat treatment of alloy ribbons has been carried out by a heat treatment method in which the alloy ribbon is heated from room temperature to a temperature 30 to 100°C lower than the temperature at which the FeB compound begins to precipitate, at a temperature rising rate of 10°C/sec or more, and then maintained for several seconds.
However, in the case of an alloy ribbon in which the Cu and Nb content is reduced and the Fe content is increased in order to obtain a high saturation magnetic flux density, the temperature difference between the bccFe (αFe) crystallization start temperature and the FeB compound precipitation start temperature becomes small, and the optimum heat treatment temperature range becomes very narrow. This causes a problem that the heat treatment temperature (maximum temperature) must be adjusted within a narrow temperature range. Furthermore, when a wide alloy ribbon having a width of 50 mm or more is produced, variations in the rapid solidification state in the width direction, variations in thickness in the width direction, and variations in composition from lot to lot occur, which further narrows the optimum heat treatment temperature range, making it difficult to perform uniform heat treatment throughout the entire alloy ribbon.

In the heat treatment of the alloy ribbon disclosed herein, temperature T1 is set to a temperature 10 to 140°C lower than the bccFe (αFe) crystallization onset temperature, and temperature T2 is set to a temperature 30 to 120°C lower than the FeB compound precipitation onset temperature. Preferably, the alloy ribbon is heated from room temperature to temperature T1 at a heating rate of 50°C/sec or higher, and then heated from temperature T1 to temperature T2 at a heating rate slower than the heating rate to temperature T1 and equal to or lower than 400°C/sec, followed by cooling. Cooling may be continued after temperature T2 is reached, or the alloy ribbon may be held at a temperature between temperature T2-50°C and temperature T2 for 0.5 to 60 seconds after reaching temperature T2, followed by cooling.

Here, the temperature rise rate is the average temperature rise rate between the temperatures. For example, the temperature rise rate from room temperature to temperature T1 can be calculated by subtracting room temperature (25°C) from temperature T1 as the numerator and the time (seconds) from room temperature to temperature T1 as the denominator.
According to the heat treatment method for an alloy ribbon of the present disclosure, a soft magnetic alloy ribbon having a high saturation magnetic flux density and low core loss can be stably produced.
The heat treatment of the alloy ribbon according to the present disclosure can also be performed after the alloy ribbon is processed into a magnetic core shape. This magnetic core shape may be a ribbon obtained by processing the alloy ribbon into a magnetic core shape by pressing or the like, a magnetic core obtained by stacking ribbons in the magnetic core shape, or a wound core formed by winding a ribbon.

Fig. 1 shows an example of a heat treatment pattern according to an embodiment of the present disclosure and a reference example of a heat treatment pattern. Fig. 2 (reference example of a heat treatment pattern) and Fig. 3 (one embodiment of the present disclosure) show correlations between the holding temperature at that time on the X axis and the magnetic flux density _B8000 when a magnetic field of _{8000 A/m is applied and the iron loss (CL) at 1 T, 1 kHz on the Y axis. Table 1 (reference example of a heat treatment pattern) and Table 2 (one embodiment of the present disclosure) show the heat treatment conditions and the B8000} and iron loss values. The alloy composition of this sample is the same as No. 3 in Table 3 described below, and the bccFe (αFe) crystallization start temperature is 470°C and the FeB compound precipitation start temperature is 590°C.

As shown in FIG. 2 and Table 1, in the heat treatment patterns of Reference Examples C1 to C5, when the holding temperature was 480°C and 490°C, B ₈₀₀₀ was 1.82 T, and when the holding temperature was 470°C or less and when the holding temperature was 500°C, B ₈₀₀₀ was less than 1.82 T. When the holding temperature was 500°C, the iron loss was significantly high. When the holding temperature was 480°C and 490°C, B ₈₀₀₀ was 1.82 T or more, and low iron loss was also obtained. However, the temperature range in which low iron loss could be obtained with B ₈₀₀₀ of 1.82 T or more was about 10°C, which was very narrow.

On the other hand, as shown in Figure 3 and Table 2, in the heat treatment patterns of Examples E1 to E6 of the present disclosure, the temperature T1 is 10°C lower than the bccFe (αFe) crystallization onset temperature (470°C), and the temperatures T2 of E1, E2, E3, E4, E5, and E6 are, respectively, 110°C, 100°C, 90°C, 80°C, 70°C, and 60°C lower than the FeB precipitation onset temperature (590°C). In the heat treatment patterns E1 to E6, the T1 holding time was 0 seconds, and the T2 holding time was 0.5 seconds.

In the heat treatment patterns of Examples E1 to E6 of the present disclosure, when the temperature T2 (holding temperature) was 490 to 530°C, _B8000 exhibited a fairly stable high value of 1.82 to 1.83 T, and when the temperature T2 was 480°C, _B8000 also exhibited a high value of 1.81 T. Furthermore, when the temperature T2 (holding temperature) was 480 to 530°C, the iron loss was 7.2 to 15.5 W/kg, indicating a low iron loss value. From this, it can be seen that the temperature range of the holding temperature where _B8000 was 1.82 T or higher and the iron loss was 25 W/kg or less was 40°C or higher, and the temperature range of the holding temperature where _B8000 was 1.81 T or higher and the iron loss was 25 W/kg or less was 50°C or higher.

In other words, with the heat treatment pattern disclosed herein, a soft magnetic alloy ribbon with high saturation magnetic flux density and low core loss could be obtained over a wider temperature range than the reference example.

The samples obtained using the heat treatment pattern of one embodiment of the present disclosure had a structure in which crystal grains with a grain size of 60 nm or less were present in the amorphous phase. Furthermore, when the cross-sections of each sample were observed, the area ratio of crystal grains with a grain size of 60 nm or less was 50% or more (value assuming the observed field area as 100%). In Figure 3 and Table 2, the holding temperature is temperature T2.

A fast heating rate during heat treatment is preferable from the standpoints of ribbon productivity, the density of nuclei generated, and preventing coarsening of crystal grain size. However, if the heating rate is too fast, crystallization occurs in a short time, the amount of heat generated per unit time increases, and the ribbon temperature rises too much, resulting in the following problems: First, the ribbon reaches the FeB compound precipitation start temperature, inducing the precipitation of FeB compounds. Second, even if the ribbon does not reach the FeB compound precipitation start temperature, the temperature rises too much, accelerating the growth of crystal grain size and deteriorating iron loss.

Therefore, in the heat treatment of the present disclosure, the rate of temperature increase from the first temperature T1 is suppressed, thereby suppressing the precipitation of FeB compounds. Furthermore, by suppressing the rate of temperature increase from the first temperature T1, crystal growth can be suppressed, thereby suppressing crystal variation. As a result, in the heat treatment of the present disclosure, it is possible to suppress an increase in iron loss and improve shape defects that occur during heat treatment, such as wrinkles caused by differential shrinkage.
The rate of temperature rise from room temperature to temperature T1 is preferably as fast as possible, for example, 50°C/sec or more, preferably 200°C/sec or more, more preferably 300°C/sec or more, and even more preferably 400°C/sec or more. The rate of temperature rise from room temperature to temperature T1 may be selected depending on the capacity of the equipment.

The rate of temperature rise from temperature T1 to temperature T2 is slower than the rate of temperature rise to temperature T1. For example, it is preferable that the rate of temperature rise is slower than the rate of temperature rise to temperature T1 and is 400°C/sec or less. Preferably, the rate of temperature rise is slower than the rate of temperature rise to temperature T1 and is 200°C/sec or less, more preferably, the rate of temperature rise is slower than the rate of temperature rise to temperature T1 and is 150°C/sec or less, and even more preferably, the rate of temperature rise is slower than the rate of temperature rise to temperature T1 and is 100°C/sec or less. Furthermore, the rate of temperature rise from temperature T1 to temperature T2 is preferably 10°C/sec or more, more preferably, 30°C/sec or more, and even more preferably, 50°C/sec or more.

As described above, the soft magnetic alloy ribbon of the present disclosure is heat-treated at a fast heating rate up to a temperature T1 that is lower than the temperature at which the temperature rise due to the crystallization of bccFe (αFe) begins. The heating rate from temperature T1 onward is then slower than the heating rate up to that point, and is set to 400° C./sec or less. This controls the heat generated by crystallization, thereby suppressing the precipitation of FeB compounds and the grain growth of αFe crystals.
In the soft magnetic alloy ribbon of the present disclosure, the heat treatment method of the present disclosure can widen the optimum heat treatment temperature range at which a high saturation magnetic flux density and a low iron loss can be obtained, and the temperature range to be controlled is widened, thereby making it possible to obtain a soft magnetic alloy ribbon with excellent heat treatability.

In the soft magnetic alloy ribbon of the present disclosure, when the density of the alloy ribbon before heat treatment is M1 and the density of the alloy ribbon after heat treatment is M2, it is preferable that M2/M1 be 1.005 or greater. The above-described heat treatment of the present disclosure can improve the density of the alloy ribbon, thereby achieving a high saturation magnetic flux density.

The soft magnetic alloy ribbon of the present disclosure has a high saturation magnetic flux density and low iron loss. The saturation magnetic flux density is 1.74 T or more, and the iron loss is 25 W/kg or less at 1 kHz and 1 T. The iron loss is preferably 18 W/kg or less, and more preferably 15 W/kg or less. The saturation magnetic flux density is preferably 1.75 T or more, and more preferably 1.77 T or more.
Furthermore, the soft magnetic alloy ribbon of the present disclosure preferably has a density of 7.45 g/cm ³ or more. When the density is 7.45 g/cm ³ or more, the volume fraction of nanocrystals increases, and the saturation magnetic flux density increases.

Furthermore, the soft magnetic alloy ribbon disclosed herein preferably has a saturation magnetostriction of 20 ppm or less. This makes it easier to achieve isotropy.

The soft magnetic alloy ribbon of the present disclosure has the configuration and characteristics of the soft magnetic alloy described above. Since the description thereof is redundant, the description above applies.
Furthermore, the soft magnetic alloy ribbon of the present disclosure preferably has a thickness of 15 μm or more, more preferably 20 μm or more, more preferably 25 μm or more, and even more preferably 30 μm or more. For example, a thickness of 25 μm or more can reduce the number of steps and manufacturing costs when laminating soft magnetic alloy ribbons to manufacture a magnetic core. A thickness of 32 μm or more is more preferable. Furthermore, if the thickness of the soft magnetic alloy ribbon is large, it becomes difficult to manufacture the alloy ribbon. Therefore, a thickness of 50 μm or less is preferable. A thickness of 35 μm or less is more preferable.
For applications requiring lower iron loss in a high frequency band exceeding 1 kHz, a soft magnetic alloy ribbon having a thickness of about 15 to 25 μm is preferred.

Moreover, the soft magnetic alloy ribbon of the present disclosure can obtain a high space factor. The soft magnetic alloy ribbon of the present disclosure preferably has a space factor of 86% or more. The soft magnetic alloy ribbon of the present disclosure preferably has a space factor of 88% or more. Due to the high space factor, when soft magnetic alloy ribbons are stacked, the lamination thickness can be made thinner than that of an alloy ribbon with a low space factor, even with the same number of layers, which contributes to the miniaturization of magnetic cores and components.
The space factor can be measured by the following method in accordance with JIS C 2534:2017.
Twenty ribbons cut to a length of 120 mm are stacked and set on a flat sample stage. A flat anvil with a diameter of 16 mm is placed on the stacked ribbons under a pressure of 50 kPa, and the height is measured at 10 mm intervals in the width direction. The maximum height at this time is defined as hmax (μm), and the space factor LF is calculated using the following formula.
LF (%) = sample weight (g) / density (g/cm ³ ) / hmax (μm) / sample length (240 cm) / ribbon width (cm) × 10000
In this case, the density (g/cm ³ ) is the density of the alloy ribbon after the heat treatment.

Furthermore, the soft magnetic alloy ribbon of the present disclosure preferably has a ratio (L/W) of 0.7 to 1.3 between the magnetic flux density L when a magnetic field of 80 A/m is applied in the casting direction of the soft magnetic alloy ribbon and the magnetic flux density W when a magnetic field of 80 A/m is applied in a direction perpendicular to the casting direction of the soft magnetic alloy ribbon. A ratio (L/W) of 0.7 to 1.3 makes it possible to obtain a soft magnetic alloy ribbon with high isotropy.

Generally, an alloy ribbon produced by ejecting a molten alloy onto a rotating chill roll and rapidly solidifying it has anisotropy introduced in the casting direction, which is the direction along the rotation direction of the chill roll, and corresponds to the longitudinal direction of the continuously cast alloy ribbon.
As described above, in a soft magnetic alloy ribbon in which anisotropy in the casting direction is introduced during casting, the introduced anisotropy also affects the properties after heat treatment (after heat treatment to form a nanocrystalline structure). In particular, if the volume fraction of the amorphous phase is high, the magnetic flux density differs between the casting direction of the alloy ribbon (the longitudinal direction of the alloy ribbon) and the direction perpendicular to the casting direction (the direction perpendicular to the longitudinal direction, which corresponds to the width direction of the alloy ribbon), and the anisotropy remains even after heat treatment.

However, there are also applications that require isotropic soft magnetic alloy ribbons, such as motor applications, etc. Therefore, it is preferable to perform heat treatment to increase the volume fraction of nanocrystals so that the difference in magnetic flux density between the casting direction and the direction perpendicular to the casting direction falls within a certain range.
On the other hand, if the heat treatment temperature is increased or the heat treatment time is extended in order to increase the volume fraction of nanocrystals, FeB compounds are precipitated under certain conditions, resulting in deterioration of magnetic properties. In particular, for soft magnetic alloy ribbons with a large amount of Fe, the optimum heat treatment temperature range for achieving isotropy is narrow, and it has been difficult to obtain a soft magnetic alloy ribbon having a nanocrystalline structure that combines high saturation magnetic flux density, low core loss, and isotropy.

This disclosure solves the above-mentioned problems and makes it possible to obtain a soft magnetic alloy ribbon that combines high saturation magnetic flux density and low core loss while suppressing the precipitation of FeB compounds, and also to obtain a soft magnetic alloy ribbon that is isotropic.

The soft magnetic alloy ribbon disclosed herein has a wide optimal heat treatment temperature range for achieving the desired properties, and is highly suitable for mass production, even when considering variations during mass production. In particular, in the case of wide alloy ribbons used in motor cores, etc., temperature variations during heat treatment are likely to occur, so a wide optimal heat treatment temperature range is effective.

Generally, if variations in the heating rate or temperature occur within the alloy ribbon, it becomes impossible to control the heat generated by partial crystallization, which causes variations in shrinkage during crystallization and wrinkles in the alloy ribbon, which can lead to problems such as a decrease in the space factor when made into a magnetic core.
However, as described above, the soft magnetic alloy ribbon of the present disclosure has a wide tolerance range for temperature variations during heat treatment, and wrinkles are suppressed, and a soft magnetic alloy ribbon with a high space factor and high smoothness can be obtained.
The smoothness can be defined as (hmax-hmin)/20, where hmax is the maximum value and hmin is the minimum value of the thickness in the width direction measured when measuring the space factor. This smoothness is preferably 3 μm or less.

By using the soft magnetic alloy ribbon of the present disclosure to form a magnetic core for use in a transformer, electronic component, motor, or the like, a magnetic core with excellent characteristics can be obtained.
When forming a magnetic core, the magnetic core can be formed by cutting alloy ribbons into a predetermined shape and stacking them, by winding alloy ribbons, or by stacking and bending alloy ribbons.
The soft magnetic alloy ribbon of the present disclosure may be pulverized into powder and the powder may be used to form a magnetic core. Alternatively, powder made of the soft magnetic alloy of the present disclosure may be produced by an atomization method and the powder may be used to form a magnetic core.
Furthermore, by combining the magnetic core of the present disclosure with a winding to form a component such as a transformer, electronic component, or motor, it is possible to obtain a component with excellent characteristics. In this case, the magnetic core of the present disclosure may be combined with a magnetic core made of another magnetic material.

Example 1
The element sources were blended to obtain the compositions shown in Table 3, and the blend was heated to 1,300°C to prepare molten alloys. The molten alloys were then ejected onto a chill roll having an outer diameter of 400 mm and a width of 200 mm, rotating at a peripheral speed of 30 m/s, and rapidly solidified on the chill roll to prepare alloy ribbons. Each alloy ribbon was heat treated under the heat treatment conditions shown in Table 4 to prepare soft magnetic alloy ribbons. The widths and thicknesses of the prepared alloy ribbons are shown in Table 3. The outer periphery of the chill roll was made of a Cu alloy with a thermal conductivity of 150 W/(m K), and the chill roll was equipped with a cooling mechanism for controlling the temperature of the outer periphery.

In Tables 3 and 4, Nos. 1 to 6 correspond to the soft magnetic alloy ribbons of the present disclosure, and Nos. 51 and 52 correspond to comparative examples. Tables 3 and 4 show the B ₈₀₀₀ , core loss at 1 T/1 kHz, density, bccFe (αFe) crystallization start temperature, FeB compound precipitation start temperature, temperature T1, temperature T2, heating rate from room temperature to temperature T1, and heating rate between T1 and T2 for each sample. The heating rate from room temperature to temperature T1 was 400 to 500°C/sec. The density is the density after heat treatment.
Each of Samples No. 1 to No. 6 had a structure in which crystal grains with a grain size of 60 nm or less were present in an amorphous phase. Furthermore, when the cross section of each sample was observed, the area ratio of crystal grains with a grain size of 60 nm or less was 50% or more (value assuming the area of the observed field of view as 100%).

[bccFe (αFe) crystallization start temperature, FeB compound precipitation start temperature]
The bccFe (αFe) crystallization onset temperature and the FeB compound precipitation onset temperature vary depending on the heating rate, but the upper limit of the heating rate of a typical thermal analyzer is about 2° C./sec., and since this makes it impossible to measure the heating rate during the heat treatment of the present disclosure, the values at a heating rate of 50° C./sec. were determined by the following method, and were used as the bccFe (αFe) crystallization onset temperature and the FeB compound precipitation onset temperature.
Using a Rigaku DSC8231, the bccFe (αFe) crystallization onset temperature and the FeB compound precipitation onset temperature were measured at three heating rates of 5°C/min (0.083°C/sec), 20°C/min (0.333°C/sec), and 50°C/min (0.833°C/sec). The values were plotted with the logarithm of the heating rate on the X axis and the bccFe (αFe) crystallization onset temperature or the FeB compound precipitation onset temperature on the Y axis, and the value at a heating rate of 50°C/sec was extrapolated from the approximation curve.

The heat-treated soft magnetic alloy ribbon was used to measure the saturation magnetic flux density (B ₈₀₀₀ ), core loss, and density.
[Saturation magnetic flux density (B ₈₀₀₀ )]
A magnetic field of 8000 A/m is applied to the heat-treated single sheet sample using a DC magnetization characteristic tester manufactured by Metron Giken Co., Ltd., and the maximum magnetic flux density at that time is measured and designated as B _8000. The soft magnetic alloy ribbon of the present disclosure has a characteristic that is relatively prone to saturation, and therefore is saturated when a magnetic field of 8000 A/m is applied, and B ₈₀₀₀ and the saturation magnetic flux density have almost the same value, so the saturation magnetic flux density is represented by B ₈₀₀₀ .
[Iron loss]
The iron loss of the heat-treated single sheet samples was measured using an AC magnetic measuring device TWM18SR manufactured by Toei Kogyo Co., Ltd. under the conditions of a magnetic flux density of 1 T and a frequency of 1 kHz.
〔density〕
Using a dry density meter AccuPyc 1330 manufactured by Shimadzu Corporation, a core-shaped sample having dimensions that could be inserted into a sample cell with an outer diameter of 17 mm and a height of 33 mm was prepared by the constant volume expansion method, and its volume was measured. The density was calculated by dividing the weight of the core by its volume.

In the examples (Nos. 1 to 6) of the present disclosure, high saturation magnetic flux density and low core loss were obtained. In addition, the density was 7.45 g/cm ^or more.
Comparative Example No. 51 has a low saturation magnetic flux density.
Comparative Example No. 52 had slightly higher iron loss but almost the same characteristic values as the Examples of the present disclosure. However, due to the low Si content, rust occurred within a few days of storage in the air, causing handling issues.

Table 5 shows the ratio (L/W) of the magnetic flux density L when a magnetic field of 80 A/m is applied in the casting direction of samples No. 1-6, 51, and 52 to the magnetic flux density W when a magnetic field of 80 A/m is applied in a direction perpendicular to the casting direction, as well as M2/M1, where M1 is the density of the alloy ribbon before heat treatment and M2 is the density of the alloy ribbon after heat treatment.

[Magnetic flux density L, W]
Using a DC magnetization characteristic tester manufactured by Metron Giken Co., Ltd., a magnetic field of 80 A/m was applied to the heat-treated single plate samples in the casting direction and in a direction perpendicular to the casting direction, and the maximum magnetic flux densities at that time were designated L and W, respectively, and isotropy was evaluated by the ratio L/W of L to W.

In the examples (Nos. 1 to 6) of the present disclosure, the ratio (L/W) was in the range of 0.7 to 1.3, and soft magnetic alloy ribbons with high isotropy were obtained, and the density ratio (M2/M1) was 1.005 or more.
Comparative Examples Nos. 51 and 52 had a ratio (L/W) exceeding 1.3.

The saturation magnetostriction values of Nos. 1 to 5 are shown in Table 5.
[Saturation magnetostriction]
A 5 kOe magnetic field was applied to a sample with a strain gauge attached by an electromagnet, and the electromagnet was rotated 360°, changing the direction of the magnetic field applied to the sample by 360°. The maximum change in the elongation and contraction of the sample was measured from the change in the electrical resistance of the strain gauge. Saturation magnetostriction was defined as 2/3 x maximum change.
The examples of the present disclosure had a saturation magnetostriction of 20 ppm or less.

Figure 4 shows a cross-sectional photograph of the soft magnetic alloy ribbon No. 2. Figure 4 is a transmission electron microscope (TEM) image observed using a transmission electron microscope. As shown in Figure 4, the soft magnetic alloy ribbon of the present disclosure has a structure comprising nanocrystals with grain sizes of 20 to 30 nm, and since nanocrystal grains account for more than half of the observed cross section, it was confirmed that the volume fraction of nanocrystals was 50% or more.

Example 2
The element sources were blended to give a composition of Fe _83.07 Si _2.20 B _13.60 Nb _0.45 Cu _0.68 , and the molten alloy heated to 1300°C was ejected onto a chill roll with an outer diameter of 400 mm and a width of 300 mm rotating at a peripheral speed of 30 m/s, and rapidly solidified on the chill roll to produce an alloy ribbon. Each alloy ribbon was heat treated under the heat treatment conditions shown in Table 7 to produce a soft magnetic alloy ribbon. The width and thickness of the produced alloy ribbon are shown in Table 6. The outer periphery of the chill roll was made of a Cu alloy with a thermal conductivity of 150 W/(m·K), and the chill roll was equipped with a cooling mechanism for controlling the temperature of the outer periphery.
Each of Samples No. 7 to No. 9 in the examples of the present disclosure had a structure in which crystal grains having a grain size of 60 nm or less existed in an amorphous phase. Furthermore, when the cross section of each sample was observed, the area ratio of crystal grains having a grain size of 60 nm or less was 50% or more (value assuming that the area of the observed field of view is 100%).

Tables 6 and 7 show the heat treatment conditions for each sample, and the results of measuring the space factor, smoothness, B ₈₀₀₀ , iron loss, and density of the sample after heat treatment.
Samples No. 53 and 54 are comparative examples. Sample No. 53 was heat-treated at a temperature T2 150°C lower than the FeB compound precipitation start temperature, and Sample No. 54 was heat-treated at a temperature T2 20°C lower than the FeB compound precipitation start temperature. The results are also shown in Tables 6 and 7. Sample No. 53 had a low _B8000 of 1.73 T, indicating insufficient heat treatment. Sample No. 54 showed a significant increase in core loss, making it impossible to measure under the conditions of 1 T and 1 kHz. This suggests that the characteristics of Sample No. 54 were degraded due to the precipitation of FeB compounds. Furthermore, Sample No. 54 developed wrinkles during heat treatment, resulting in a space factor of 79% and a smoothness of 3.5 μm.
The examples (Nos. 7 to 9) of the present disclosure had high saturation magnetic flux density, low iron loss, and a space factor of 86% or more. They also had high density and good smoothness.

[Occupancy rate]
Measurements were carried out according to the following method in accordance with JIS C 2534:2017.
Twenty ribbons cut to a length of 120 mm are stacked and set on a flat sample stage. A flat anvil with a diameter of 16 mm is placed on the stacked ribbons under a pressure of 50 kPa, and the height is measured at 10 mm intervals in the width direction. The maximum height at this time is defined as hmax (μm), and the space factor LF is calculated using the following formula.
LF (%) = sample weight (g) / density (g/cm ³ ) / hmax (μm) / sample length (240 cm) / ribbon width (cm) × 10000

As described above, according to the present disclosure, a soft magnetic alloy ribbon having a high saturation magnetic flux density and low core loss has been obtained. Furthermore, according to the present disclosure, a soft magnetic alloy ribbon having suppressed anisotropy and isotropy has been obtained. Furthermore, according to the present disclosure, a soft magnetic alloy ribbon having a high density, a high space factor, and good smoothness has been obtained. The soft magnetic alloy ribbon of the present disclosure is one embodiment of the soft magnetic alloy of the present disclosure.

When a magnetic core is constructed using the soft magnetic alloy ribbon of the present disclosure, it can be constructed using known means. Furthermore, a magnetic core constructed using the soft magnetic alloy ribbon of the present disclosure is constructed with the high saturation magnetic flux density, low core loss, and isotropy inherent to the soft magnetic alloy ribbon of the present disclosure, resulting in a magnetic core with excellent characteristics.

Furthermore, by constructing a component including a magnetic core made using the soft magnetic alloy ribbon of the present disclosure and a winding, a component having the high saturation magnetic flux density, low iron loss, and isotropy that the soft magnetic alloy ribbon of the present disclosure has can be constructed, and a component having excellent characteristics can be obtained.

Claims (10)

_{A soft magnetic alloy ribbon having an alloy composition represented by a composition formula (Fe1-xAx)aSibBcCudMe , wherein A is at least} one of Ni and Co, and M is at least one selected from the group consisting of Nb, Mo, V, Zr, Hf, and W, and the atomic percentages of the soft magnetic alloy ribbon are 82.4≦a≦86, 0.2≦b≦2.4, 12.5≦c≦15.0, 0.05≦d≦0.8, 0.4≦e≦1.0, and 0≦x≦0.1,
The soft magnetic alloy ribbon has a structure in which crystal grains having a grain size of 60 nm or less are present in an amorphous phase , and the area ratio of the crystal grains calculated from an image of a cross section observed with a transmission electron microscope is 50% or more, the width is 50 mm or more, the space factor is 86% or more, the saturation magnetic flux density is 1.74 T or more, and the iron loss at 1 kHz, 1 T is 25 W/kg or less. The soft magnetic alloy ribbon according to claim 1 , having a density of 7.45 g/cm ³ or more. 3. The soft magnetic alloy ribbon according to claim 1 , wherein the thickness of the soft magnetic alloy ribbon is 25 μm or more. 4. The soft magnetic alloy ribbon according to claim 1 , wherein a ratio (L/W) of a magnetic flux density L when a magnetic field of 80 A/m is applied in a casting direction of the soft magnetic alloy ribbon to a magnetic flux density W when a magnetic field of 80 A/m is applied in a direction perpendicular to the casting direction of the soft magnetic alloy ribbon is 0.7 to 1.3. 5. The soft magnetic alloy ribbon according to claim 1 , wherein the saturation magnetostriction is 20 ppm or less. A method for producing the soft magnetic alloy ribbon according to any one of claims 1 to 5 ,
A method for producing a soft magnetic alloy ribbon having a structure in which crystal grains having a grain size of 60 nm or less exist in an amorphous phase by heat-treating an alloy ribbon,
In the heat treatment, a temperature T1 is set to be 10 to 140°C lower than the bccFe crystallization start temperature, and a temperature T2 is set to be 30 to 120°C lower than the FeB compound precipitation start temperature.
Heat from room temperature to temperature T1 at a temperature increase rate of 50°C/sec or more,
Heating from temperature T1 to temperature T2 at a temperature rise rate that is slower than the temperature rise rate up to temperature T1 and is 400° C./sec or less,
Cooling after reaching temperature T2, or
After reaching temperature T2, the soft magnetic alloy ribbon is held at a temperature between temperature T2-50°C and temperature T2 for 0.5 to 60 seconds, and then cooled. 7. The method for producing a soft magnetic alloy ribbon according to claim 6, wherein the alloy ribbon before the heat treatment is obtained by ejecting a molten alloy onto a rotating chill roll and rapidly solidifying it on the chill roll, and an outer periphery of the chill roll is made of a Cu alloy having a thermal conductivity of 120 W/(m K) or more. 8. The method for producing a soft magnetic alloy ribbon according to claim 6 , wherein M2/M1 is 1.005 or more, where M1 is the density of the alloy ribbon before the heat treatment and M2 is the density of the alloy ribbon after the heat treatment. A magnetic core formed using the soft magnetic alloy ribbon according to any one of claims 1 to 5 . A component comprising the magnetic core according to claim 9 and a winding.